The present invention relates to highly efficient encoding of analog video signals to digital data carrying a less amount of data for effident data transfer, storage and displaying. More specifically, this invention relates to encoding of interlaced moving picture signals with bidirectional inter-picture prediction.
Highly efficient encoding of moving pictures with inter-picture prediction includes the following three methods:
(1) Encoding independently a specific frame among xe2x80x9cmxe2x80x9d frames (m being an integer of two or more) entirely without reference to the other frames;
(2) Encoding frames by uni-directional prediction using a preceding specific frame; and
(3) Encoding frames by bidirectional prediction using preceding and upcoming specific frames.
These encoding method are disclosed in U.S. Pat. No. Re. 34,965 published on Jun. 13, 1995.
Pictures, or frames to be subjected to this encoding method are of three different picture types, that is, I frames (intra-coded frames), P frames (predictive-coded frames) and B frames (bidirectionally predictive-coded frames). Locally decoded I and P frames are used for interframe prediction, however, B frames are never used as reference frames for prediction.
Interlaced signals are composed of even fields and odd fields. The even and odd fields are displaced from each other by {fraction (1/60)} sec., or by one scanning line.
MPEG-2 standards, for example, employs a method of encoding for each field by using a plurality of fields as reference fields or a method, a combination of major encoding for each frame and subsidiary encoding for each field. The picture types (I, P and B) in MPEG-2 standards are always decided for each frame. This means that, even in encoding for each field, I and P fields are decided by means of two successive fields.
In any method described above for encoding interlaced signals, prediction is carried out for each field whenever displacement occurs between fields due to the movement of picture. Pictures composed of fields and carried by interlaced signals include many aliasing components. Effective inter-picture prediction thus cannot be carried out. In detail, inter-picture prediction produces relatively many predictive errors even if an object in a picture is just displaced right or left without vertical movement.
A purpose of the present invention is to provide an apparatus and a method of encoding/decoding moving picture signals that achieve effective inter-picture prediction and discrete cosign transform, and also a storage medium that stores the encoded moving picture signals.
The present invention provides an apparatus for efficiently encoding a moving picture signal. The encoding apparatus includes a first encoder, a predictor and a second encoder. The first encoder encodes progressively scanned specific frames that exist for every predetermined period in a moving picture signal to be encoded by infra-frame processing or by uni-directional prediction using other encoded specific frames and by orthogonal transform at the 2n-th (n being an integer) order in a vertical direction. The predictor predicts frames or fields of the moving picture signal other than the specific frames by using a preceding reference frame and/or an upcoming reference frame, thus producing a predictive error signal for each field. And, the second encoder encodes the predictive error signal for each field by orthogonal transform at the 2nxe2x88x921-th order in the vertical direction.
Furthermore, the present invention provides an apparatus for efficiently decoding a moving picture signal. The decoding apparatus includes a first decoder, a second decoder and a predictor. The first decoder decodes specific frames that exist for every predetermined period in a moving picture bit stream to be decoded by inverse orthogonal transform at the 2n-th (n being an integer) order in a vertical direction and by infra-frame processing or by uni-directional prediction using other encoded specific frames, thus reproducing a moving picture signal for each progressively scanned frame. The second decoder decodes a predictive error signal of frames or fields of the moving picture bit stream other than the specific frames by inverse orthogonal transform at the 2nxe2x88x921-th order in the vertical direction. And, the predictor predicts the frames or fields of the moving picture signal other than the specific frames by using a preceding reference frame and/or an upcoming reference frame, thus reproducing a moving picture signal.
Moreover, the present invention provides a method of efficiently encoding a moving picture signal. Progressively scanned frames that exist for every predetermined period in a moving picture signal are encoded by infra-frame processing or by uni-directional prediction using other encoded specific frames and by orthogonal transform at the 2n-th (n being an integer) order in a vertical direction. Frames or fields of the moving picture signal other than the specific frames are predicted by using a preceding reference frame and/or an upcoming reference frame, thus producing a predictive signal for each field. And, the predictive signal for each field is encoded by orthogonal transform at the 2nxe2x88x921-th order in the vertical direction.
The present invention further provides a method of efficiently decoding a moving picture signal. Specific frames that exist for every predetermined period in a moving picture bit stream are decoded by inverse orthogonal transform at the 2n-th (n being an integer) order in a vertical direction and by infra-frame processing or by uni-directional prediction using other encoded specific frames, thus reproducing a moving picture signal for each progressively scanned frame. A predictive error signal of frames or fields of the moving picture bit stream is decoded other than the specific frames by inverse orthogonal transform at the 2nxe2x88x921-th order in the vertical direction. And, the frames or fields of the moving picture signal are predicted other than the specific frames by using a preceding reference frame and/or an upcoming reference frame, thus reproducing a moving picture signal.
The present invention also provides a storage medium storing efficiently encoded moving picture bit stream. Alternatively stored in the storage medium are a first bit stream and a second bit stream. The first bit stream has been produced by encoding progressively scanned specific frames that exist for every predetermined period in a moving picture signal to be encoded by infra-frame processing or by uni-directional prediction using other encoded specific frames and by orthogonal transform at the 2n-th (n being an integer) order in a vertical direction. And, the second stream has been produced by predicting frames or fields of the moving picture signal other than the specific frames by using a preceding reference frame and/or an upcoming reference frame, thus producing a predictive error signal for each field and encoding the predictive error signal for each field by orthogonal transform at the 2nxe2x88x921-th order in the vertical direction.